Linker Error: undefined reference to `vtable`

Hi! I am trying to compile and start testing an agent based simulation of a zombie apocalypse, however I use inheritance and I keep getting a linker error that says, exactly: "[Linker error] undefined reference to `vtable for Human'" Any guidance or help would be very much appreciated, as most of the `vtable problems I find on the net seem either not to be the same situation or aren't answered. I will keep looking however. Thanks in advance!